PhD study trip
Daou - A traditional alcoholic fermentation starter
Food fermentation is of great importance in Chinese life and culture. A wide variety of traditional fermented foods are produced in semi-controlled conditions. Chinese liquor is one of the world’s oldest distilled alcoholic beverages, and plays an important role in Chinese culture and people’s daily life.
The liquor is made from cereals, mainly sorghum, by fermentation, distillation and maturation. Mixed culture starters, which are locally called “Daqu”, are used as inoculum for the solid-state fermentation (Zheng et al., 2011). The manufacture of Daqu by traditional uncontrolled fermentation techniques results in products with inconsistent quality; this causes large losses of unsuccessful products which go to waste as animal feed. Therefore standardization of the Daqu production process is an important objective for Chinese liquor producers.
Aim
The aims of this research project are (1) to assess the diversity of microbiota in different types of Daqu; (2) to investigate the succession of microbiota during production of Daqu; and (3) to understand the physio-ecology of microorganisms in Daqu and their relation to formation of metabolites and other flavour compounds.
Research
In the first part of this project Daqu samples from different factories will be collected in order to investigate the differences of microbial composition in different flavour of Daqu using cloning techniques. In the second part conventional and advanced microbiological techniques will be used for isolation, quantification and characterization of the occurrence of functional microorganisms in different stages of Daqu making processes. Relevant physical-chemical properties will be studied to investigate the succession of microbiota in relation to the environment. The information will be used to open the secret of traditional Daqu making, and stimulate the modernization, standardization and optimization of Daqu making.
Future research
Different functional microbial formulation will be tested during alcoholic fermentation, the function of each selected microorganism will be determined by comparing their growth, metabolites production and enzyme activities.
Conclusion
Although the manufacturing techniques have been modernized during recent years, the inconsistency and instability of Daqu is still a problem that hampers the standardization of Chinese liquor making. Our study will provide qualitative and quantitative information on the microbial diversity present in Fen-Daqu and its microbial evolution process. The knowledge of microbial composition and functionality will enable further upgrading of the Chinese traditional Daqu making processes, e.g. by selection of functionally important strains, and optimization of microbial composition and quality control.